It's also the most confused idea of a currency yet. Its basic idea is derived from the gold standard idea, to rebirth the concept that it somehow 'grounds' the currency in contrast to the alleged 'menace' of fiat currencies. Note well that the majority of Bitcoin enthusiasts are libertarian cranks who believe in the obsolete religion of money supply control and the view that massive currency issue limitation is achieved not by balancing it against resource availability, but scarcity of 'magic metal'; or in their case the intangible version.
On the other hand, a sensible assessment would ask why the hell any currency-issuing entity would want to put itself in a situation where it runs out of its own currency? Of course the Bitcoiners and their friends think it prevents the resurrection of their oft-named nemeses: 'Weimar Germany' and 'Zimbabwe', apparently the poster boys for demonstrating the fiat currency threat of hyperinflation (in a situation where governments have issued more currency in the last 10 years than in entire preceding 50 years and still fight deflation!!).
Plus they are also anti-government everything and would prefer, as TheFlash indicated, to have private little black markets for their activities, largely because they don't understand the functions of tax and think it is mainly for penalising rich people or anyone really. Bitcoin is a toy anyway, witness how many measure its worth by referring to how much they could, in principle, convert into dollars/pounds etc as a measure of their amazing Bitcoin wealth. It is, therefore, a value measured in fiat currencies, which they all ultimately know sustains the actual financial side of the economy.